Steam-gage



E. G. ALLEN.

Steam Pressure Gauge.

Patented May 1, 1860."

UNITED STATES PATENT OFFICE.

ENOS G. ALLEN, OF BOSTON, MASSACHUSETTS.

STEAIVLGAG-E.

Specification of Letters Patent No. 28,045, dated May 1, 1860.

To aZZ whom it may concern:

Be it known that I, E. G. ALLEN, of Boston, in the county of Suffolk andState of Massachusetts, have invented certain new and usefulImprovements in Steam-Gages; and I do hereby declare that the followingdescription, taken in connection with the accompanying drawingshereinafter referred to, forms a full and exact specification of thesame, wherein I have set forth the nature and principles of my said improvements, by which my invention may be distinguished from all othersof a similar class, together with such parts as I claim and desire tohave secured to me by Letters Patent.

The figures of the accompanying plate of drawings represent myimprovements.

Figure 1 is a plan or top view of my improved stea1n-gage. Fig. 2 is alongitudinal central vertical section of the same. Fig. 3 is a plan ortop view of my improved spring. Figs. 4; and 5 are views in detail.

I have heretofore made certain improve ments in steam-gages for whichLetters Patent of the United States were granted to me hearing date the17th day of January, 1860, in which a volute spring, tapering in widthonly was the medium used for transmitting the pressure of the steam tothe index-hand. Vhile this form of spring has been found to operatesuccessfully and with accuracy for ordinary pressures its form will notallow sufliciently thick steel to be used for very heavy pressuressayfrom 500 pounds to the square inch upwardand consequently when subjectedto very great strains these kinds of springs do not possess therequisite strength to prevent their being warped or otherwise injured.In cases where perfect accuracy is not of so much consequence asstrength, as in machines or the various apparatus used in mechanicswhich are to be tested with regard to their strength so as to guardagainst the danger of explosion or collapsing, for instance, andsubjected to an enormous pressure or a much greater one than they are toreceive while actually in use, the importance of having a spring thatwhile having sufliciently accurate powers of indicating for the purpose,shall also be of such a form as to possess great strength and retain itspowers without injury during repeated tests, will be evident.

To so construct a volute spring in a steam gage as to possess theserequisites of great strength and with sufficiently accurate indicatingfunctions for purposes where only great pressures are to be applied isone of the essential features of the present invention, the desiredresults being attained by the use of a volute spring of uniform widthand tapering only in thickness. This form of spring allows thicker andheavier steel to be used than would otherwise be possible andconsequently can be made so as to possess great strength and also hasproved to be sufticiently accurate for the purposes for which its use isintended. I have also made an i1nprovement which consists in insertingbetween the rubber which I have heretofore employed in combination withthe volute spring, a thin flexible plate of metal which obviates adifficulty that has been experienced from the cutting and wearing out ofthe rubber diaphragm by coming in contact with the edges'of the coils ofthe spring.

My last improvement relates to the mechanism that constitutes the mediumfor com municating the movements of the spring, produced by the pressurethereon, to the index-hand, whereby the gage can be readily connected incase of error, adapted to heavy and light pressures, &c., and consistsin rendering the length of the indicating arm so as to vary at pleasurethe leverage and consequently the length of movement communicated fromthe spring to the index-hand.

a a in the drawings represents the box in which the devices whereby themovement of the spring is transmitted to the indicator are placed.

I) Z) is a volute spring, Figs. 2 and 3, placed in two boX couplings cand (Z. These couplings are firmly screwed together, a shoulder e of thecoupling (Z being thus brought to.

bear upon the outer coil of the spring and holding it rigidly so as toprevent any play or friction between the spring and the boxcouplings,while at the same time the remaining portion of the spring is leftperfectly free to act. The volute sprin 6 b is of peculiar shape, asshown in the drawings, being formed of a bar of steel of uniform widththroughout and tapering in thickness only, as shown in Figs. 4 and 5. Itwill be seen by inspection of Fig. 5 that the end of the bar of steel ofwhich the spring is composed that is to bear upon the shoulder e of thecoupling (Z commences with an increasing taper for a short distance andthen diminishes to the requisite thickness at the end which is to formthe smallest coil, the part with an increasing taper at the larger endbeing only for the purpose of a true bearing surface upon and to be heldby the boxcouplings o and (Z which hold the spring in its place, thisportion of the coil not acting as a spring. The outer coil of the springbeing held by the shoulder e of the coupling cl, the inner or smallestcoil is fastened to a short shaft or piston Steam is admitted to thespring I) Z) through the short tube g, forming a part of the boxcoupling 0 and in order that the pressure of'the steam may be exertedequally upon all portions of the spring 6 b, a disk or diaphragm ofrubber h, or other suitable elastic material Fig. 2 is inserted betweenand held by the two boxcouplings 0 and (Z in such a manner as toentirely cover the outer surface of the spring, a thin plate of metal,represented by a blue line in Fig. 2, being inserted between the rubberdiaphragm and the spring, to prevent the wearing and cutting away of therubber disk as invariably happens when the rubber is in direct contactwith the coils of the spring.

I will next proceed to describe the devices which form the medium forcommunicating the movement of the spring produced by the pressure of thesteam to the indicator. To the short shaft or piston f which is fastenedto the inner and smallest coil of the spring Z) 6 is attached aconnecting rod 6 i. The rod 71, i is attached by a pivot joint Z, to ashort arm m attached to the sector shaped arm a, turning upon a bearingat 0. The short arm m turns upon a center at z and can be set at anydesired angle with regard to the sector shaped arm n by means of a slot79 and set-screw g, as shown by red lines in Fig. 1, thereby diminishingor increasing the lever power brought to bear upon the indicator 1", atpleasure. Thus the connecting rod 2' and arm 172, form thelong arm of alever of which the sector shaped arm n is the short arm and 0 thefulcrum. The end of the sector-shaped arm n terminates in a geared are.9 that engages with a pinion t retracted by a coil spring u. The piniont is attached to the spindle w, upon which is fastened the indicator T.It will be seen from this description that the movement of the volutespring Z) 6, is imparted to the indicator 1", through the levers i 2'and n thereby indicating the exact pressure of the steam upon the spring6 6.

Having thus described my improvements 1 shall state my claim as follows:

hat I claim as my invention and desire to have secured to me by LettersPatent is l. The use in gages for indicating the pressure of steam orother fluids of a volute spring, the coils of which are of uniform widththroughout and which taper in thickness only, in combination with therubber and metallic disks or diaphragms as set forth.

2. The thin flexible metallic disk interposed between the rubberdiaphragm and the outer surface of the coils of the volute spring, forthe purpose specified.

E. G. ALLEN.

\Vitnesses:

JOSEPH GARRETT, A. W. BROWN.

